Stirred Reverberation Chamber Research Articles

An Effective Parameter to Characterize the Rician Channel in Hybrid Stirred Reverberation Chamber

An Effective Parameter to Characterize the Rician Channel in Hybrid Stirred Reverberation Chamber

Modeling of electromagnetic propagation inside jet engine environment using statistical electromagnetic approach

In this paper, the distribution of the electromagnetic field inside a complex jet engine environment is analyzed using statistical electromagnetics. The jet engine environment is an extremely complex geometry and exhibits random behavior due to the presence of moving metallic parts. This renders traditional analytical and simulation modeling techniques highly inefficient. To address this issue, two different approaches are proposed to model the propagation characteristics of the jet engine environment. The first is an innovative dynamic system approach based on dynamic system simulation which is inspired by the analysis of mechanically stirred reverberation chambers. In the dynamic system simulation the dynamic system, which is characterized by the rotation of a distinct set of blades, is primarily studied through the simulation program. A dimension scaling method is also introduced along with the dynamic system simulation to solve the complex jet engine environment. In the second approach, a novel statistical excitation method is applied to develop an equivalent model for the dynamic jet engine system. The studied jet engine is considered as a static jet engine system without blade rotation (static blades), but with a random excitation.A small signal analysis method is used to integrate the static and dynamic system parameters to generate random excitation characteristics of the static system. The extracted electric field values from the dynamic jet engine simulation environment and the static system field values from the small signal analysis have been analyzed statistically to prove the statistical equality between the two systems. The numerical results of the static system model are presented and verified through comparison with finite element method simulation packages.

Emission Test Method for Source Stirred Reverberation Chambers With Scalar Measurements

This paper describes a novel method to reconstruct the radiated emission of a device under test placed in a reverberation chamber equipped with multiple monopole source stirring technique. The method is based on the measurement of the normal component of the electric field, collected close to the walls of the chamber by the monopole antennas. The main improvement from the previous formulation of the method is that the only knowledge of the amplitude of the electric field is sufficient to reconstruct, within a predictable range of uncertainty, the maximum level of the radiation of the device over all the directions at a given distance. The consequent advantage is that the method is immediately usable in a realistic scenario for emission tests, where an EMI receiver or a spectrum analyzer are used to measure the electric field and therefore only the amplitude of the field is retrieved.

Emulation of the Rician K-Factor of 5G Propagation in a Source Stirred Reverberation Chamber

This paper presents a novel algorithm to emulate the Rician K-factor of a wireless communication environment using a reverberation chamber. In particular, it was focused on the frequency bands used by 5G technology for data transmission. Unlike the current state of the art, the increase of the Rician K-factor is not achieved by inserting lossy material in the chamber, but through the proposed algorithm, which selects a subset of electromagnetic field realizations inside the chamber. The algorithm was first applied to the results of a simulation obtained by using an analytical model that predicts the main physical quantities inside a rectangular cavity where a multiple monopole source stirring action is implemented. Subsequently, the robustness of the algorithm and its applicability was tested on a set of data retrieved from experimental measurements. In all of the considered scenarios, the validity of the proposed method was demonstrated.

A general method for radiated emission prediction in a multiple monopole source stirred reverberation chamber

This paper presents a general and quasi-analytical method aimed at reconstructing the electric field radiated by equipment under test (EUT), in free space through the knowledge of the values of the electric field sampled on the walls of a rectangular metallic enclosure. The algorithm is based on a set of equivalent magnetic and electric currents, regularly placed in a sub volume of the chamber, whose values are determined to reconstruct the electric field due to the EUT on the samples. Results show that the method is general because it can be applied to a wide set of EUTs, but it is also flexible because it is able to exploit some a priori knowledge of the source to improve its accuracy and efficiency.

Statistics of the Current Induced Within a Partially Shielded Enclosure in a Reverberation Chamber

The statistics of the current induced on conducting wires and surfaces within a partially shielded enclosure by aperture coupling of an ideally random, mechanically stirred reverberation chamber electromagnetic field has been considered. A robust discretization of the plane-wave spectral representation of the chamber field confirms that the magnitude of the induced current at a test point follows a Rayleigh distribution provided that the equipment under test (EUT) is composed entirely of electromagnetically linear materials and mechanical or spatial stirring of the external chamber field is used, independent of the sizes of the EUT and coupling aperture. The discrete spectrum gives an efficient method to numerically find the statistics of the currents on or within arbitrarily shaped EUTs. Experimental measurement of the induced currents on a sample EUT within a mechanically stirred reverberation chamber confirms the validity of the discrete-plane-wave spectral method of predicting the current statistics at low and high frequencies. Addition of frequency stirring introduces a fundamental difference in the operation of a reverberation chamber test that leads to non-Rayleigh sample statistics when highly resonant EUTs are considered.

Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida

It is now accepted that plants perceive high-frequency electromagnetic field (HF-EMF). We wondered if the HF-EMF signal is integrated further in planta as a chain of reactions leading to a modification of plant growth. We exposed whole small ligneous plants (rose bush) whose growth could be studied for several weeks. We performed exposures at two different development stages (rooted cuttings bearing an axillary bud and 5-leaf stage plants), using two high frequency (900MHz) field amplitudes (5 and 200Vm−1). We achieved a tight control on the experimental conditions using a state-of-the-art stimulation device (Mode Stirred Reverberation Chamber) and specialized culture-chambers. After the exposure, we followed the shoot growth for over a one-month period. We observed no growth modification whatsoever exposure was performed on the 5-leaf stage plants. When the exposure was performed on the rooted cuttings, no growth modification was observed on Axis I (produced from the elongation of the axillary bud). Likewise, no significant modification was noted on Axis II produced at the base of Axis I, that came from pre-formed secondary axillary buds. In contrast, Axis II produced at the top of Axis I, that came from post-formed secondary buds consistently displayed a delayed and significant reduced growth (45%). The measurements of plant energy uptake from HF-EMF in this exposure condition (SAR of 7.2 10−4Wkg−1) indicated that this biological response is likely not due to thermal effect. These results suggest that exposure to electromagnetic field only affected development of post-formed organs.

Estimate of the Probability Density Function of the Quality Factor of Mode Tuned, Source Stirred and Mode Stirred Reverberation Chambers

The probability density function (PDF) of the quality factor Q of well-stirred mode tuned, source stirred, and mode stirred reverberation chambers (STRCs, SSRCs and MSRCs, respectively) is derived. The approach is based on the volumetric number of independent field samples, and a new physical model is introduced to estimate the ratio between the stored energy and the dissipated power, so that the stirring speed is taken into account for MSRCs. The ergodicity of the spatial-correlation function of the energy density in the chamber volume is initially assumed; in other words, the independent sample number of the energy density, which contributes to the Q , is assumed to initially be constant for each field distribution across the volume. Then, this assumption is relaxed and the theory is enhanced to the case where the size of the independent volumetric samples is considered random, as well as their number. By invoking the central limit theorem, the Q PDF is achieved. It is shown that the Q PDF is basically normal, and its standard deviation decreases with the increasing of the independent variables that contribute to the Q itself. The Doppler effect tends to increase the standard deviation of the Q PDF.

UHF RFID tags backscattered power measurement in reverberation chamber

Presented is a methodology for measuring the power backscattered by ultra-high frequency radio frequency identification (UHF RFID) tags by using a modes stirrer reverberation chamber. The actual measurement methodology is described and its advantage and disadvantage against the conventional setup using anechoic chambers are outlined. Then, some results of power measurements performed with the three Gen2 class 1 tags are presented. The experimented tags' sensitivity and radiation efficiency as a function of incident power are finally derived. The results are very encouraging and demonstrate the feasibility of such a characterisation in modes stirred reverberation chambers. All the measurements were carried out at a single frequency of about 866 MHz.

频率搅拌嵌套混响室场分布的统计特性

频率搅拌嵌套混响室场分布的统计特性

Statistical investigation and experimental verification of frequency stirring reverberation chamber

A statistically uniform E-field can be created in a reverberation chamber by frequency stirring. The statistical properties of frequency stirring reverberation chamber in over-moded are analyzed, and the ideal probability density functions (PDF) of E-field and field power are presented. In order to verify the statistical model, the S21 parameter which is the normalized power is measured between transmitting and receiving antenna. The result of the examination and processed data shows that the histogram of S21 can be good agreement with the theoretical model when the number of sample is enough.

混响室的混沌特性及其场统计分布

Quantum chaos theory is used to study a reverberation chamber (RC). We evaluate the chaotic characteristics of a numerical RC by analyzing the eigenfrequency spacing distribution with the finite element method. Based on the electromagnetic chaotic features and the hypothesis, the electric field vector eigenfunction in the RC could be expressed as linear superposition of random plane waves. Then the electric field in the RC can be expressed as the vector eigenfunction expansion. The Rayleigh distribution model of probability density function of electric field in the RC is derived by statistical approach. The electric field intensity measurement in an actual mechanical stirring RC is completed with ETS HI-6105 prober. The electric field distribution in the chamber is in close agreement with the result from the statistical model, which proves the validity of the theoretical model.

Design and Testing of an Antenna System for the Source Stirring Technique in Reverberation Chambers

The paper describes the design and testing of a radiating structure developed to reverberate electromagnetic fields in shielded chambers. The radiating system consists of a set of conical broadband wire antennas, adapted to cover the operational frequency range of 1 to 3GHz. Twenty antennas are used to build up the structure, and field stirring is achieved by switching on 190 different combinations that generate field statistics and field uniformity quite similar to those of a mechanically stirred reverberation chamber (RC). All the measurements prescribed by standard and literature were carried out to test the stirring capabilities of the radiating structure, and to assess that the RC field fulfills the IEC 61000-4-21 requirements.

混响室的概率统计分析方法及其蒙特卡罗模拟

混响室的概率统计分析方法及其蒙特卡罗模拟

Human keratinocytes in culture exhibit no response when exposed to short duration, low amplitude, high frequency (900 MHz) electromagnetic fields in a reverberation chamber

We exposed normal human epidermal keratinocytes to short duration, high frequency, and low amplitude electromagnetic fields, similar to that used by mobile phone technologies. We paid particular attention to the control of the characteristics of the electromagnetic environment generated within a mode stirred reverberation chamber (statistical homogeneity and isotropy of the field and SAR distribution). Two non-thermal exposure conditions were tested on the epidermal cells: 10-min exposure with a field amplitude of 8 V/m, and 30 min with 41 V/m. Corresponding specific absorption rates ranged from 2.6 to 73 mW/kg (continuous wave, 900 MHz carrier frequency). We collected RNA from cells subjected to these conditions and used it for a large-scale microarray screening of over 47000 human genes. Under these conditions, exposure of keratinocytes to the electromagnetic field had little effect; only 20 genes displayed significant modulation. The expression ratios were very small (close to 1.5-fold change), and none of them were shared by the two tested conditions. Furthermore, those assayed using polymerase chain reaction did not display significant expression modulation (overall mean of the exposed samples: 1.20 ± 0.18). In conclusion, the data presented here show that cultured keratinocytes are not significantly affected by EMF exposure.

The Role of Losses in the Definition of the Overmoded Condition for Reverberation Chambers and Their Statistics

It is commonly acknowledged that in perfectly stirred reverberation chambers, the energy density of the electric field follows a X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> law, as long as the overmoded condition applies. This concept, never defined properly, is often confused with the idea of a threshold on the modal density, regardless of the quality factor of the cavity. This interpretation is here proven to be inaccurate, as losses play a fundamental role in the nature of the field statistics and not, as often assumed, just in its scaling. In particular, it is shown how the overmoded condition should be stated mathematically, highlighting how the cavity quality factor and the number of eigenmodes excited cannot be regarded as quantities intervening independently on the field statistics, but should rather be considered jointly. These results are derived by means of a modal analysis, with a limited number of assumptions. A quantitative relationship is established between average modal overlapping and the rate of convergence of the electric energy density towards a X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> law. Rather than setting an arbitrary threshold on modal overlapping as a necessary condition for an overmoded behavior, the statistical uncertainty due to the limited number of available field samples is shown to affect the very definition of the overmoded condition.

The prediction of the electric field level in the reverberation chamber depending on position of stirrer

This study presents nine modeling techniques within data mining process for the prediction of electric field level which depends on the positions of stirrer in the mode stirred reverberation chamber. These are Linear Regression (LR), Multi Layer Perceptron (MLP), Pace Regression (PR), KStar, Regression by discretization (RD), Random SubSpace (RS), M5P, RepTree and Decision Table models. Relations depending on frequency and position of stirrer have been carried out for the determination of electric field in the reverberation chamber. Obtained model results for each stirrer steps have been compared and the best model has been investigated. Results indicate that the use of derived formulation from these techniques will facilitate design and optimize of location of maxima (mode) and minima (null) of electric field in the reverberation chamber which a component of especially mode stirrer reverberation chamber test method.

General regression neural network approach to prediction of electric field level in the reverberation chamber

This study presents an approach for the prediction of electric field level which depends on the positions of stirrer and frequency in the mode stirred reverberation chamber. A general regression neural network (GRNN) is used for prediction process. In order to show the system performance, feature selective validation (FSV) technique is given. The simulation results show that the predicted values of electrical field have been obtained with high accuracy. Thus, this technique will facilitate estimation of electric field level in the reverberation chamber which is component of especially mode stirrer reverberation chamber test method.

Coupled reverberation chambers for emulating MIMO channels

Abstract This article describes a new experimental set up for emulating MIMO channels, based on two mode stirred reverberation chambers (MSRC), coupled together with a waveguide. This guide allows one to control the order of the channel diversity, the chambers generating a Rayleigh environment. This set up could thus be used to perform tests of MIMO communication systems in perfectly defined environments and thus under reproducible conditions. After a brief recall of the advantages and drawbacks of using a single reverberation chamber, we describe the theoretical approach and the experimental results for the analysis of two coupled chambers.

MODE STIRRED REVERBERATION CHAMBER (MSRC): A LARGE AND EFFICIENT TOOL TO LEAD HIGH FREQUENCY BIOELECTROMAGNETIC IN VITRO EXPERIMENTATION

An important aspect of the studies undertaken in bioelectromagnetism relates to the choice of exposure facility. The characteristics of a real electromagnetic environment are far more complex compared to the one plane wave irradiation set-up used in the majority of bioelectromagnetic studies. Moreover, biological requirements should represent the starting point in the design of an in vitro exposure system. Indeed it is important to avoid altering the electromagnetic properties of the exposure system in the presence of biological equipments. Related to these two essential points, this article contributes to show the advantages of a Mode Stirred Reverberation Chamber (MSRC) to guarantee a controlled electromagnetic environment around biological materials for in vitro experimentation. An example of irradiation of in vitro human skin cells cultures is considered to illustrate this paper. In order to show that the biological conditions and the physical requirements for in vitro experiments are checked, two aspects are described. Firstly we achieved the characterization of the electromagnetic fleld generated around the biological system (both equipments and cultures). Secondly the analysis of the Speciflc Absorption Rate (SAR) inside the biological medium was evaluated both numerically and experimentally. Initially,